1. Field of the Invention
This invention relates to an electric powered bicycle having a DC motor for use as an auxiliary power source, a dip sensor or switch for detecting a dip of a chain and/or a gradient sensor or switch.
2. Description of the Prior Art
An auxiliary power unit or bicycle having a DC motor for use as an auxiliary power source is applied by the present inventor in accordance with Japanese Patent Application No. 62-97083, laid open for public inspection as JP-A-63-263189.
In FIG. 1, a DC motor control circuit for use in a bicycle (FIG. 2) comprises a DC motor 1 having its output shaft meshed with a chainset of the bicycle. A power supply voltage from a battery 2 can be supplied to the DC motor 1 through an emitter-collector of a power transistor 3. A collector and a base of the power transistor 3 are connected to a base and a collector of a detection transistor 6 through resistors 4 and 5, respectively. An emitter of the detection transistor 6 is grounded through a switch 7.
Therefore, even if the switch 7 is turned on, transistors 6 and 3 maintain an OFF state unless the DC motor 1 is not rotating. When an external force causes the rotation of a rotor of the DC motor 1, induced voltage pulses generated between brushes of the DC motor 1 exceeding a predetermined level are applied to the base-emitter of the detection transistor 6. Then the transistors 6 and 3 are sequentially turned on to transfer their latch conditions.
An output of a pulse generator 8 which generates periodical pulses is ORed to the base of the detection transistor 6 through a transistor 9. The power supply for the pulse generator 8 is controlled by another transistor 11, and is maintained by a smoothing capacitor 12 upon instantly turning the transistor 11 off. The pulse generator 8 produces output pulses each instantly turning off the detection transistor 6 to turn off the power transistor 3. The detection transistor 6 detects the collector voltage of the power transistor 3 still in an OFF state just after the output pulse returns to the normal level. When the DC motor 1 is rotating, it generates an induced voltage or potential to again turn on the detection transistor 6, which turns on the power transistor 3 so as to maintain the rotation of the DC motor 1 by supplying power thereto.
The DC motor 1 or M is mounted on a frame 21 of the bicycle as shown in FIG. 2. In this case, an output shaft of the DC motor M is rotatably coupled to the chainset or front sprocket 23 through a gearbox G. Therefore, as a younger or aged driver continues pedalling on a pedal 24, the bicycle is moving and the shaft of the DC motor M is rotating through the chainset 23 and gearbox G. With the DC motor rotation, electric power is supplied to the DC motor M to transfer an auxiliary rotational power of the DC motor M to the chainset 23 and to the rear wheel 26 through a chain 25. A freewheel 27, chain 25, chainset 23, pedal 24 and other constructions of this bicycle are identical to those of a conventional bicycle. The switch 7 as shown in FIG. 1 is mounted on the frame 21 to detect a dip of the chain 25. Then, as the driver stops the pedalling action on the pedal 24, the upper side components of the chain 25 are slung down to shut off the power supply of the DC motor M.
However, in the control circuit described above, since the ON/OFF operation of the DC motor 1 is based on the pedalling action on the pedal 24, the power supply to the DC motor 1 performs with wasted energy consumption when the pedal 24 continues to be pedalled on a flat or downhill run.
When the auxiliary power is actuated on a downhill road, extreme acceleration of the bicycle may be provided to produce an uncontrollable speed. It is therefore preferable to activate the auxiliary power on a steep ascent of the road.